If they are under a year they are still teething and this could last for a while. Do they have something like a Nylabone to chew on? I would take away the disposable pads and use washable ones until this behavior stops...or...put them in crates and crate train them instead of using the x-pen. I don't usually recommend washable pads but if they are destroying the disposable ones you have to try something else so it's either crate training or washable pads. You might try one of the sprays for your trim and walls...something like Bitter Apple...you spray it on the spot and supposedly they leave it alone.
P.S. I don't want to make light of your frustration or make a joke out of the situation but...if your pups are getting your 'crown moulding' I would say you have other, more serious issues to deal with...my crown moulding goes around the top of my rooms
